Many applications exist for high intensity illuminators which are capable of producing a field of illumination which varies from a narrow field to a relatively wide field. Some such applications require the capability of varying such a field in different increments from narrow to wide or simply switch between a narrow field and a wide one.
One such application is an image enhancement device for utilization with infrared image intensifiers used in night vision equipment. Night vision direct view image intensifiers generally are found in two distinct classes. One class, with no amplification, is referred to as generation zero or as a component of generation one devices. The second class, with inherent amplification, is referred to as a generation two device. There is a generation three device, but as far as this discussion is concerned, generation three devices are no different from generation two devices. Generation zero and generation one devices have optical gains limited to magnitudes of about one-hundred (100). Therefore, if such devices are to be used in a dark environment, they need to be coupled together; so that the individual optical gains may be multiplied. Such a coupling results in a bulky, awkward and expensive device. Generation two devices, because of the inherent amplification, may have optical gains in the thousands and thus, generation two devices are very useful for night vision environments. However, even though generation two devices are much less bulky and awkward than coupled generation zero or one devices, generation two devices are very expensive. To permit the utilization of generation zero or generation one devices in low light environments, some type of illuminator or light enhancement is necessary.
Another area where high intensity visible light of variable width fields is useful is in conjunction with camera flash units. Most camera flash devices which currently are marketed, have a fixed and relatively wide light spread for the light emanating from the flash unit. Capacitor discharge circuits are employed for providing power to a high intensity flash lamp in popular electronic flash devices currently employed with most modern cameras. Such flash devices either are provided as add-on units for the camera or now are built into the camera. Older flash units employ flashbulbs and reflectors. In such units the flashbulb is expended each time a flash picture is taken. The reflectors typically have a fixed shape for a relatively wide angle reflection of the light from the flashbulb.
Another application of varying light focus is found in automobile headlights. Typically, automobile headlights are provided with a "low" beam and a "high" beam mode of operation. For some headlights, the two functions are combined in a single lamp; and the beam location is varied in accordance with the location of the beam filaments with respect to the reflector to provide either the high or low beam illumination from the head lamp. In many automobile headlight systems, two separate pairs of lamps are provided. The "low" beam lamp set is focused at a first range or spread of light and the second "high" beam lamp set is focused for a different range and illumination spread. The headlight systems are operated in the same manner by the operator of the automobile who simply selects one or the other of the two different modes of operation through the manipulation of a selection switch.
High intensity light emitting devices, such as laser diodes and the like, presently are well known and are utilized in many applications. Such devices are relatively small and operate on a low amounts of power. The light intensity of laser diodes operating both in the visible and infrared spectrums is high; so that if a lens system is devised which is capable of dispersing or spreading the narrow beam of light from a laser light source, illumination at different angles may be achieved. It is desirable to provide such a system which is capable of changing the illumination from a high intensity light source, such as a laser light source, from a narrow collimated beam to a wide uniform beam. Additionally, it is desirable to provide such a system which is self focusing throughout the range from the narrowest beam to the widest beam obtainable.